1. Field of the Invention
The present invention relates to a photoacoustic measurement device, that is, a device that radiates light to a subject, such as a body tissue, detects an acoustic wave generated by the light irradiation, and performs measurement related to the subject.
In addition, the invention relates to a probe used for the photoacoustic measurement device.
2. Description of the Related Art
Photoacoustic imaging devices have been known which image the inside of a living body using a photoacoustic effect, as disclosed in, for example, JP2005-21380A and JP2009-31268A or “A High-Speed Photoacoustic Tomography System based on a Commercial Ultrasound and a Custom Transducer Array,” Xueding Wang, Jonathan Cannata, Derek DeBusschere, Changhong Hu, J. Brian Fowlkes, and Paul Carson, Proc. SPIE Vol. 7564, 756424 (Feb. 23, 2010). In the photoacoustic imaging device, for example, pulsed light, such as pulsed laser light, is radiated into the living body. In the living body irradiated with the pulsed light, the body tissue absorbs the energy of the pulsed light, the volume of the body tissue is increased by heat, and the body tissue generates acoustic waves. Then, the acoustic waves are detected by, for example, an ultrasonic probe and the inside of the living body is visualized on the basis of an electric signal (photoacoustic signal) obtained from the acoustic waves.
In many cases, the probe which is used for the photoacoustic measurement device, such as the photoacoustic imaging device, also has a function of emitting light to be radiated to the subject. In this case, it is desirable to radiate the flux of light with uniform intensity to the part to be imaged in the subject. For example, as described in JP2009-31268A, it is considered that light is incident on a light guide and the flux of light emitted from the light guide is radiated to the subject.
The light guide is configured such that the total reflection of light is repeated therein and the intensity distribution of irradiation light is uniform. In general, the light guide has a parallel plate shape and includes two side surfaces which are parallel to each other, a light incident end surface on which light is incident, and a light emission end surface which is opposite to the light incident end surface, with the side surfaces interposed therebetween, and from which light is emitted.